| Summary: | 碩士 === 國立彰化師範大學 === 科學教育研究所 === 88 === To approach the active site of the〔Fe〕-only hydrogenases, isolated from D. desulfuricans and C. pasteurianum, structural model compound, we try to synthesize some Fe(Ⅱ)-thiolate cyanocarbonyl compounds－complex 1 , complex 3, complex 4, complex 5 characterized by IR, NMR, UV and X-ray diffraction.
The reaction of 〔PPN〕〔Fe（CO）4（CN）〕 with 2-aminophenyl disulfide yielded pentacoordinate, sixteen-electron FeⅡ complex〔PPN〕〔Fe（CO）2（CN）（S, NH-C6H4）〕(1), stabilized by strong S, Nπ-donation of chealting 〔S, NH-C6H4〕2- ligand. Protonation of complex 1 by electrophiles（2-mercaptopyrimidine and 2- aminophenylthiol）yielded hexacoordinate Fe(Ⅱ)-thiolate cyanocarbonyl complexes 〔PPN〕〔Fe（CO）（CN）（S-C4H3N2）2〕(5) and〔PPN〕〔Fe（CO）2（CN）（S-C6H4NH2）（S, NH2-C6H4）〕(3) respectively. The IR spectrum of complex 5 in the aprotic solven CH3CN displayed a weakυ(CN) band at 2090 cm-1 and strongυ(CO) band at 1945 cm-1. Chemical oxidation of complex 5 in CH3CN at -20。C with 〔Cp2Fe〕〔PF6〕displayed absorption bands at 2096 and 1962 cm-1 which were assigned toυ(CN) andυ(CO) vibrational frequencies of thermally unstable neutral FeⅢ（CO）（CN）（S-C4H3N2）2 respectively. Complex 5 was reobtained upon addition of〔PPN〕〔BH4〕to FeⅢ（CO）（CN）（S-C4H3N2）2 in CH3CN at -20。C.
The first dinuclear Fe(Ⅱ)-thiolate cyanocarbonyl compound 〔PPN〕〔（CN）（CO）2 Fe（μ-S, S-C6H4）〕2 (4) was prepared by reaction 1, 2-benzenedithiol with complex 1 in THF at -10。C. Complex 4 is the promoising structural and functional model compound of the active centers of〔Fe〕-only hydrogenases isolated from D. desulfuricans and C. pasteurianum. The X-ray structure analysis shows that complex 4 possesses crystallographically imposed centrosynnetry. Two hexacoordinate Fe(Ⅱ) center are connected via two thiolate bridges, and both CN- ligands point into the antiparallel direction. The IR spectrum of complex 4 in the aprotic solvent CH2Cl2 revealed a strong absorption bands for CO groups at 1960, 2013 cm-1 and a weak absorption band for CN- groups at 2101cm-1. When CH2Cl2 solution of complex 4was exposed to 13CO(g) at 0。C, absorbances at 1968, 1915 cm-1 appeared within 10 minutes. Reappearance of the 2013, 1960 cm-1 bands on removal of the 13CO(g) and replacement with 12CO(g) atomosphere demonstrated reversibility of CO ligand lability of complex 4.
The vibrational spectroscopy of the Fe（CO）2（CN）and Fe（CO）（CN） fragments（υ(CN) range from 2094 to 2105 cm-1; υ(CO) ranges from 1928 to 2013 cm-1 ）found in complexes 1, 3, 4, 5 may be regarded as spectroscopic references of 〔Fe〕 hydrogenases in the various enzymatic states.
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